1. Field of the Invention
The present invention relates to a feeder assembly for a high temperature, gas-phase reactor and, more particularly, to a downstream, radially mounted, multiple injector liquid feeder.
2. Description of the Prior Art
There is currently a major effect to develop low cost solar arrays. A primary need is the rapid, high capacity production of good quality silicon at a nominal cost. Present state-of-the art manufacturing processes for producing high purity silicon are generally carried out at temperatures below 1100.degree. C. and are necessarily multi-step in order to separate co-products and to improve purity, when necessary, and for melting and ingot casting. An example of one of these processes is the Siemens-Westinghouse process where trichlorosilane is reduced by hydrogen at a temperature of 950.degree. C. Silicon is then collected by deposition on a surface or rod. Production rates are normally of the order of 10 grams/hr.
A high temperature process is under development in which silicon is produced as a liquid, the co-products are gaseous and the reaction times are very short for the gaseous reactants. Therefore, high silicon production rates may be achieved in relatively small reaction chambers and the liquid silicon be collected and directly cast into ingots. The co-product gases can be recovered and recycled. Electric arc heaters may be utilized to supply heat to a carrier gas such as an argon-hydrogen mixture to heat the reactants to the desired reaction temperature; i.e. 2000.degree.-2200.degree. K.
A stream of reducing agent such as a Group I or II metal, particularly sodium, magnesium or zinc, and a stream of vaporized or atomized SiCl.sub.4 reactant are injected concurrently into the carrier gas plasma, are vaporized and react to form high purity liquid silicon and by-product gaseous salt according to the following basic reaction, when assuming a sodium reactant: EQU 4Na+SiCl.sub.4 .fwdarw.Si(1)+4NaCl(g)
The by-product salt produced and the carrier gas can be recycled after the silicon has been separated. This process can be run in a batch or continuous mode. The reactor system includes an axial section for injection of the reductant into the arc-heated plasma, a downstream reactor section including a SiCl.sub.4 injection system, a reaction and particle growth section and a separation and product collection assembly. The reactor section has an equilibrium wall (skull wall) of solid silicon. The injection of SiCl.sub.4 must be accomplished in a manner which does not cool the inner wall below the temperature necessary for the equilibrium skull wall.
The introduction of SiCl.sub.4 must also be conducted in a manner to promote rapid dispersion and mixing in the reductant stream so that the reaction can take place quickly and completely. The preferred method of introduction of SiCl.sub.4 is as liquid by means of a hydraulic atomizing nozzle. The introduction of SiCl.sub.4 as a gas would not provide complete mixing since a significant portion of the SiCl.sub.4 gas stream would be deflected by the axially flowing reductant stream.